We happen to see this one approximately from its equatorial plane (approx.
left-to-right in our image); this is similar to our view of another, fainter
Messier planetary nebula, M76, which is called the
Little Dumbbell. From near one pole, it would probably have the shape of a
ring, and perhaps look like we view the Ring Nebula
M57.

This planetary nebula is certainly the most impressive object of its kind
in the sky, as the angular diameter of the luminous body is nearly 6 arc
minutes, with a faint halo extensing out to over 15', half the apparent
diameter of the Moon (Millikan 1974). It is
also among the brightest, being at most little less luminous with its
estimated apparent visual magnitude 7.4 than the brightest, the Helix
Nebula NGC 7293 in Aquarius, with 7.3,
which however has a much lower surface brightness because of its larger
extension (estimates from Stephen Hynes); it is a bit unusual that this
planetary is only little fainter photographically (mag 7.6).
The present author (hf) was surprized how fine this object was seen in his
10x50 binoculars under moderately good conditions !

As measured by Soviet astronomer O.N. Chudowitchera from Pulkowo
(and mentioned by L.H. Aller, Glyn Jones and Vehrenberg),
the bright portion of the nebula is apparently expanding at a rate
of 6.8 arc seconds per century, leading to an estimated age of 3,000 to 4,000
years, i.e. the shell ejection probably would have been observable this time
ago (it actually happened earlier as the light had to travel all the distance
of perhaps about 1000 light years). She estimated the distance somewhat short
at only about 490 ly.
Another estimate, given by Burnham, has obtained a rate 1.0 arc seconds per
century, and an estimated age of 48,000 years.

The central star of M27 is quite bright at mag 13.5, and an extremely hot
blueish subdwarf dwarf at about 85,000 K (so the spectral type is given as
O7 in the Sky Catalog 2000).
K.M. Cudworth of the Yerkes Observatory found that it probably has a faint
(mag 17) yellow companion at 6.5" in position angle 214 deg (Burnham).

As for most planetary nebulae, the distance of M27 (and thus true dimension
and intrinsic luminosity) is not very well known. Hynes gives about 800,
Kenneth Glyn Jones 975, Mallas/Kreimer 1250 light years, while other existing
estimates reach from 490 to 3500 light years. Currently, investigations
with the Hubble Space Telescope are under work to determine a more reliable
and acurate value for the distance of the Dumbbell Nebula.

Adopting our value of 1200 light years,
the intrinsic luminosity of the gaseous nebula is about 100 times that of the
Sun (about -0.5 Mag absolute) while the star is at about +6 (1/3 of the Sun)
and the companion at +9..9.5 (nearly 100 times fainter than the Sun), all in
the visual light part of the electromagnetic spectrum.
That the nebula is so much brighter than the star shows that the star emits
primarily highly energetic radiation of the non-visible part of the
electro-magnetic spectrum, which is absorbed by exciting the
nebula's gas, and re-emitted by the nebula, at last to a good part in the
visible light. Actually, as for almost all planetary nebulae, most of the
visible light is even emitted in one spectral line only, in the green light
at 5007 Angstrom (see our
planetary nebula description) !